I need to obtain my keys out of the trunk of a 2005 Jagar XJ ?

You can use the key on the trunk the key aperture is at the right side of the trunk. Hopefully it is not seized from lack of use. As you turn the key try thumping the boot above the top of the back edge with your hand not too hard and also rocking the car by the boot

i am not sure what black key your refering to but all you have to do is put the car in the trunk and it should open,once open vallet will disengage.

Look for a trunk release inside the passenger's compartment on the driver's side, or in glovebox.

from memory there was no switch you had a green key that woild only fit the ign and drivers door the black key fitted all doors glove locker and trunk

Look under the boot handle near the number plate light and you'll see a hole where you can use your key to open the boot.

Wether it is an xk or xj, you cannot get to the trunk by removing the back seat, the gas tank is in the way.
Where the badge/decal is that says either XJ8 or XK8 there is a key hole in the badge so you can open the trunk.
The most common problem with the auto trunk opening is the actual harness in the right far corner of the trunk, the wires are not long enough and become stressed and eventually fracture causing an open circuit and no power to the remote opening.
Hope this helps
JPTCAT

read your manuel, there are 3 different locations the key can be removed from and this eliminates theft if valet is used. when removed in a certain clock position, I don't remember which one but I had to look it up it locks

2000 jag trunk locked dead battery-use MASTER KEY ONLY to open trunk location is above rear lic plate looks like hex screw ---the valet key will not open trunk-you cannot go thru back seat thr release for them are in the trunk-hope this helps someone

the battery has gone dead you can not open the boot/trunk with the electrical system but you should be able to get to the battery by using the key in the lock on the outside of the the trunk its either in the xj badge or the number plate illumination holder. if you can open the engine compartment there is battery pos power points so you can jumpstart/power up the car